Redfield b



UNITED STATES PATENT OFFICE.

REDFIELD B. WEST, OF GUILFORD, CONNECTICUT, ASSIGNOR OF ONE-HALF TO BENJAMIN C. WEST, OF SAME PLACE.

" PHOTO-GRAPHIC PRINTING.

SPECIFICATION forming part of Letters Patent No. 273,206, dated February 27, 1883.

Application filed November 17, 1882. (No specimens.)

To all whom it may concern:

Be it known that I, REDFIELD B. WEST, of Guilford, in the county of New Haven and State of Connecticut, have invented a new Improvement in Photographic Printing; and I do hereby declare the following to be a full,

clear, and exact description of the same.

My invention relates to-an improvement in the process of photographic printing, with special reference to the sensitizing ot' the paper before printing and the development of the print, the object of the invention being principally to avoid the expensive silver solution now generally employed in this class of work; and my invention consists in subjecting the paper to a bath composed of potassium bichromate, magnesium sulphate, and mercuric chloride, to sensitize the paper, and then, after the exposure of the paper for printing in the usual manner, subjecting the print for development to a bath composed of gallic acid, ferrous sulphate, aluminum and ammonium sulphate, and sodium hyposulphite, as more fully hereinafter described.

First. The bath for rendering the paper sensitive to light. I, prepare a bath as follows: Take of potassium bichromate, three parts; magnesium sulphate, one part; mercuric chloride, one part. Mix and dissolve in the smallest quantity of boiling water required for solution and crystallizing. Of this compound take seventy-five grains to each ounce of water employed in the bath. The paper isfloated in this bath for, say, three minutes, and is then dried in the dark. When required for printing it is placcd under the negative a sufiicient time to make the lighter shades in the print visible, the time varying, say, from three to ten minutes under direct sunlight. The ex- 0 posed portions of the print will be light brown upon a yellow ground. So soon as this condition is attained the paper is taken from beneath the negative and soaked in pure Water, say,t'ortwentymiuutes. Ifthenegativebevery intense, such as to require ten or more minutes of direct exposure to the sunlight, the soaking should be continued longer-say to about half an hour. This is desirable, because itfacilitates the subsequent developing. The 0 excess of bichromate being removed leaves the whites of a faint yellow tint. Where pure whites are required it becomes necessary to destroy all traces of bichromate where the light has not acted, and which are not easily removed by soaking. For this purpose the print is immersed in one per cent. solution of acid sulphite of sodium for one or two minutes.

To prepare the developer,'l take of gallic acid, two parts; ferrous sulphate, three parts; aluminum and ammonium sulphate, three parts; sodium hyposulphite, twenty-fourparts. The ferrous sulphate, aluminum and ammonium sulphate, and sodium hyposulphite are each dried separately until free from water of crystallization, and are then pulverized and 55 mixed with the gallic acid. This compound will keep and retain all its properties if protected from dampness. Of this composition take fifteen grains to each ounce of water. To develop the print, lay it in'a suitable dish and pour upon it the developing solution to cover it, say, quarter of an inch in depth; or, if several prints are to be developed at the same time, take enough of the solution to cover all the prints. While they are in the solution 5 move them frequently, so as to expose them equally to thedeveloping solution. When the development of the print is completed, which will generally require about ten minutes, the excess of the developer absorbed by the paper is removed by soaking the print for half an hour in water slightly acidulated with acetic acid, after which, and when dry, the picture can be mounted. It s subsequent treatment may be substantially that usually applied to photographic prints. The sodium hyposulphite and alum in the developer exerta reducing action, which prevents the ferrous salt from becoming oxidized readily when in solution and exposed to the air, and enables the 0 bath to be used repeatedly for several days, if after use the precaution is taken of putting it in a tightly-corked bottle, which should be filled by the solution.

Any color from black to brown can be ob- 5 tained,after soaking out the developer, by immersing the print from one to five minutes in a bath composed of one part taken from the sensitizing-bath to two parts of water, the time of contact with the bichromate determining rco the shade, and after such treatment soak in water until the yellow tintis entirely removed.

If desired to change the color of a print to reddish brown, subject it, after development, to a bath composed of a solution of carbonate of soda (one ounce carbonate to one quart water) and dry immediately.

In case it be necessary to bleach the picture, it should be done after development and before any change of color is effected, and may be well done by subjecting the print to a solution of one partcitrate of ammonia in twenty parts of water.

The paper may be prepared for sensitizing by any of the known processes; but I find a very good result is obtained from the following treatment: Take paper of a good quality, coat it with a mixture composed of starch, seven parts; white sugar,two parts; glycerine, two parts; boiling water, two hundred parts; and solution of pure caustic potash, suflicient to cause the coating to dry with an even surface, which will require about one-fourth part potash. The first three ingredients are mixed with a little cold water and then stirred into the boiling water. The coating is applied by floating the paper upon the mixture in the manner usually employed in the application of albumen to paper. After drying, the paper is dipped in a two per cent. solution of acetic acid and water, and when again dried it is ready for use. In cases where the intensity and appearance of the print are of little importance, paper may be used without this treatment. Albumen paper does not under my improved process produce so good results, chiefly on account of its density.

From my experiments I believe the proportions for the sensitizing and developing baths above given produce the best results; but these proportions may be varied to some extent without departing from my invention.

By-this process I am enabled to produce photographic prints fully equal to those produced by the employment of silver; and it will be evident to those skilled in this art that the cost of the production is very much less than by the usual process employing nitrate of silver. The printing is also more rapid than by the usual process, and colors may be more readily applied to the print than when the print is prepared under the usual process.

I claim 1. The herein-described improvement in the process of photographic printing, consisting in subjecting the paper to be printed upon to a bath composed of potassium bichromate, magnesium sulphate, and mercuric chloride, in the proportions and substantially as described. V

2. Theherein-described improvement in photographic printing, consisting in subjecting the print to a bath composed of gallic acid, ferrous sulphate, aluminum and ammonium sulphate,and sodium hyposulphite, in the proportions and substantially as described.

3. The herein-described improvement in the process 'of photographic printing, consisting in subjecting the paper upon which the print is to be made to a bath composed Ofpotassium bichromate, magnesium sulphate, mercuric chloride, and then, after printing, to a bath composed of gallic acid, ferrous sulphate, aluminum and ammonium sulphate, and sodium hyposulphite, in the manner, and the said baths in the proportions, substantially as described.

REDFIELD B. VEST.

Witnesses BEVERLY Mormon, HENRY S. WEDMORE. 

